The present disclosure relates to a developing device for use in electro-photographic image forming apparatuses such as a copier, a printer, a facsimile machine, and a multifunction peripheral having these functions, and an image forming apparatus including such a developing device.
In image forming apparatuses, an electrostatic latent image formed on an image carrier such as a photosensitive drum or the like is developed by a developing device and visualized as a toner image. Examples of the developing device include one employing a two-component developing method, in which a two-component developer is used. In a developing device of this type, two-component developer (hereinafter, also referred to simply as developer) comprising toner and carrier is stored in a developing container, and there are arranged a developing roller, which supplies developer to an image carrier, and a stirring-conveyance member, which stirs and conveys developer in the developing container to supply the developer to the developing roller.
In a developing device employing the two-component developing method, in order to replenish toner of an amount consumed in development, it is necessary to measure toner concentration in developer by means of a toner concentration sensor disposed inside the developing container. For example, there has been proposed a developing device in which a toner concentration sensor is disposed, in a developer circulation path, on a side thereof where supply of the developer to a developing roller is performed, whereas a toner replenishment section is disposed on another side where supply of developer to the developing roller is not performed. With this configuration, the replenished toner reaches the toner concentration sensor after being sufficiently mixed with the developer inside the developing container, and accordingly the toner concentration in such a portion of the developer as is to be supplied to the developing roller can be directly detected. This helps replenish toner with further improved precision.
For maintenance of the detecting sensitivity of a toner concentration sensor, for example, there is known a method in which a scraper for cleaning the sensor surface (detection surface) of a toner concentration sensor is attached to such a portion of a stirring-conveyance member as opposes the toner concentration sensor.
On the other hand, there is known a stirring-conveyance member which includes a main conveyance blade (a first spiral blade) which conveys a developer in a first direction, which is a direction toward one side in an axial direction, along with rotation of a shaft member, and a sub conveyance blade (a second spiral blade) which produces a conveying effect in a second direction, which is a direction toward the other side in the axial direction, with respect to part of the developer, along with rotation of the shaft member. With this configuration, the sub conveyance blade causes convection in part of developer conveyed, and a stirring effect is promoted, with the conveying effect of the main spiral blade hardly inhibited.